The present invention relates to automatic control devices, provided for controlling a blind or similar device giving protection from the sun, in either of its two operating directions: unrolling and rolling up. These devices comprise an electronic comparator whereof one input is connected to a pick-up provided for measuring the intensity of a metheorological phenomenon such as: wind speed, temperature, brightness of the sun and so on, whereof a second input is connected to a device for regulating a predetermined threshold of said intensity and whereof the output is connected to control means. These control means are provided for controlling the initiation of the elapse of a first predetermined delay period and for illuminating a luminous indicator, at the instant when the intensity of the meteorological phenomenon equals or exceeds the predetermined threshold, then for controlling the operation of the blind in a first direction at the end of this first delay period. If the first delay period is terminated, they are also provided for controlling the initiation of the elapse of a second predetermined delay period, at the instant when the intensity once more drops below the predetermined threshold, then controlling the operation of the blind in a second direction, at the end of this second delay period. The function of the first and second selay periods, which have a duration of one to ten minutes for example, is to prevent excessively close, successive changes of the direction of operation of the blind, in the case where the intensity of the metheorological phenomenon oscillrates rapidly around the predetermined threshold.
In known automatic control devices of this type, the luminous indicator, which is connected directly to the output of the electronic comparator, has an operation which is linked directly and solely with the existing level of intensity of the meteorological phenomenon, with respect to the predetermined regulating threshold of this intensity. As long as this intensity is equal to or greater than this threshold, the luminous indicator is illuminated and as soon as the intensity drops below the threshold, the luminous indicator is extinguished. It follows that throughout the entire duration of the second delay period, which precedes the control of the operation of the blind in its second direction, an observer cannot know if the second delay period is in progress and if the command controlling the blind in the second direction will be given shortly, or the automatic control device is broken-down. Hitherto, the only means of knowing this consists of waiting for the end of a period at the most equal to the second delay period and of ascertaining if the blind is then effectively actuated in its second direction. The problem occures for example when the intensity detected is the intensity of the brightness of the sun. If, at a given instant, the observer ascertains that the blind is unrolled and that there is no sun, he may assume that the installation is broken-down.